The use of a roller provided with an inner annular chamber which is at least partly filled with a hot heat carrying fluid or through which a hot heat carrying fluid can circulate to heat an external cylindrical wall of the roller, which roller provides a suitable ironing surface to make contact with the articles to be ironed, is known in the art in the field of laundry machinery. The problem to be solved is how to distribute the hot heat carrying fluid inside the chamber along the roller to ensure a uniform heating of the external cylindrical wall all along the roller.
U.S. Pat. No. 4,418,486, belonging to the public domain, discloses an ironing roller with a heating device comprising two concentric cylindrical walls arranged to rotate together about a common longitudinal axis. The external cylindrical wall provides a suitable ironing surface to make contact with the articles to be ironed, and an annular chamber in communication with an inlet at a first end of the roller and with an outlet at a second end of the roller is formed between the external cylindrical wall and the inner cylindrical wall, such that the chamber forms a passage through which a heat carrying fluid heated by an external heating device can pass. Helical fins or blades are arranged in the chamber with a single rotation direction to propel the heat carrying fluid inside the chamber from said inlet to said outlet as a result of the rotation of the roller. An external circuit, to which an impulse pump is coupled, is arranged to propel the return heat carrying fluid from the outlet to the inlet of the chamber.
The mentioned U.S. Pat. No. 4,418,486 teaches how to circulate the heat carrying fluid inside the chamber from the inlet to the outlet and how to return the heat carrying fluid from the outlet to the inlet passing through heating means and an external pump. A drawback of this construction is the need to have considerable equipment outside the roller, formed by a circuit, heating means, an expansion tank, one or more pumps, etc., as well as rotary joints to connect the conduits of the external circuit to the inlet and outlet of the chamber, which joints are arranged axially through pivot joints at each end of the roller.
U.S. Pat. No. 4,677,773 describes a rotary flatwork ironer comprising a roller formed with a double wall providing a closed annular chamber for a fluid, means for rotatably supporting the roller with respect to a horizontal axis, a fluid inlet and a fluid outlet at opposite ends of the chamber, heating means arranged in a stationary manner inside the roller to heat the fluid inside the chamber, a flow circulation system to make the fluid circulate from said outlet to said inlet passing through a rotating joint and an external circuit including a pump, a cooling tank and an expansion tank, and temperature control means arranged in a part of the circulation system outside the roller and adapted to detect the temperature of the fluid and to start and stop the heating means in response to the detected fluid temperature.
Patent EP-A-1130152 discloses a drying ironing machine provided with an ironing roller with a heating device using a heat carrying fluid. The ironing roller is provided with a cylindrical wall and is suitable to rotate about an axis of said cylindrical wall. Inside the roller there are arranged conventional heating means such as those described in the mentioned U.S. Pat. No. 4,677,773 to heat the cylindrical wall. The roller further comprises an external wall surrounding the cylindrical wall in order to delimit with the latter a closed annular chamber, which is partially filled with a heat carrying fluid. The roller further comprises stirring means for stirring the fluid including members placed in said annular chamber and suitable for generating circulation of the heat carrying fluid inside the chamber according to the teachings disclosed by the aforementioned U.S. Pat. No. 4,418,486. The mentioned external wall provides an ironing surface. According to a first embodiment (FIG. 3 of the mentioned patent), said members are passive members in the form of helical blades borne by the cylindrical wall and arranged inclined with respect to the axis of the roller to generate circulation of the heat carrying fluid when the roller rotates about its axis. In two opposite halves of the roller, the helical blades have opposite rotation directions to propel the heat carrying fluid in opposite directions. According to a second embodiment, (FIG. 5 of the mentioned patent), the members are partitions arranged in a stepped manner in the annular chamber in order to delimit, between the cylindrical wall and the external wall, a zigzag back and forth path which is considerably parallel to the axis of the roller, and the stirring means further comprise a pump on the roller to make the heat carrying fluid circulate according to said path
The heating means of the roller described in the mentioned patent EP-A-1130152 dispense with any external equipment. However, a drawback of the first embodiment is that the mentioned helical blades do not ensure uniform distribution of the heat carrying fluid along the roller due to the fact the return circulation is carried out, after the collision of opposite fluid streams, mixed with the propelling circulation of the blades. If the blades propel the fluid in opposite directions towards the center of the roller during rotation, the fluid tends to accumulate in the central area of the roller. If on the other hand, the blades propel the fluid in opposite directions towards the ends of the roller, the fluid will tend to accumulate in the areas close to the ends of the roller. A drawback of the second embodiment is the need to incorporate an impulse pump on the roller, the proposed winding configuration of the fluid distribution circuit, which can be expensive to carry out, and the need of rotary electrical connections for the connecting cables for connecting the pump to an external power supply source.